阅读说明：本技术 一种肖特基二极管及其制备方法 (A kind of Schottky diode and preparation method thereof ) 是由 任娜 于 2019-08-01 设计创作，主要内容包括：本申请公开了一种肖特基二极管及其制备方法,用以解决PN结设置不合理的问题。肖特基二极管包括衬底、外延层以及金属层。外延层形成于衬底上,为第一导电类型的区域；外延层背离衬底的一侧设有若干第二导电类型的区域,第二导电类型的区域与第一导电类型的区域之间形成PN结；其中,第二导电类型的区域包括若干第一区域和第二区域,第一区域沿外延层表面的宽度大于第二区域的宽度,每两个相邻的第一区域之间设有若干第二区域,第一区域按照第一预设间隔排布,第二区域按照第二预设间隔排布；金属层形成于外延层背离衬底的一侧,外延层的表面除第二导电类型的区域之外的区域,与金属层形成肖特基结。(This application discloses a kind of Schottky diodes and preparation method thereof, to solve the problems, such as that it is unreasonable that PN junction is arranged.Schottky diode includes substrate, epitaxial layer and metal layer.Epitaxial layer is formed on substrate, is the region of the first conduction type；Epitaxial layer is equipped with the region of several second conduction types away from the side of substrate, forms PN junction between the region of the second conduction type and the region of the first conduction type；Wherein, the region of second conduction type includes several first areas and second area, first area is greater than the width of second area along the width of epi-layer surface, several second areas are equipped between every two adjacent first area, first area is arranged according to the first preset interval, and second area is arranged according to the second preset interval；Metal layer is formed in the side that epitaxial layer deviates from substrate, and region of the surface of epitaxial layer in addition to the region of the second conduction type forms schottky junction with metal layer.)

1. a kind of Schottky diode, which is characterized in that including substrate, epitaxial layer and metal layer；

The epitaxial layer is formed on the substrate, and the epitaxial layer is the region of the first conduction type；

The epitaxial layer is equipped with the region of several second conduction types away from the side of the substrate, second conduction type PN junction is formed between region and the region of first conduction type；Wherein, second conductivity type regions include several One region and second area, the first area are greater than the width of the second area along the width of the epi-layer surface, often Several second areas are equipped between two adjacent first areas, the first area is arranged according to the first preset interval, described Second area is arranged according to the second preset interval；

The metal layer is formed in the side that the epitaxial layer deviates from the substrate, and the surface of the epitaxial layer is removed described second and led Region except the region of electric type forms schottky junction with the metal layer.

2. the method according to claim 1, wherein

First preset interval determines that described second is pre- based on the width of the first area and the area of the schottky junction If the reverse leakage current size being spaced based on the diode determines.

3. the method according to claim 1, wherein

The first area forms regular polygon or circle on the surface of the epitaxial layer, and several first areas are uniformly arranged Cloth；

The second area forms ring structure around the first area on the surface of the epitaxial layer, and is directed to each firstth area Domain, several second areas are arranged successively centered on the first area, the second area between every two adjacent first area Uniformly arrangement.

4. according to the method described in claim 2, it is characterized in that,

The quantity of second area between every two adjacent first area is determined by S=P*X+N* (X+1), wherein S is institute The first preset interval is stated, P is the width of the second area, and N is second preset interval, and X is two adjacent firstth areas The quantity of second area between domain.

5. the method according to claim 1, wherein

The width of the first area is 2~21 microns, and the width of the second area is 0~3 micron.

6. according to the method described in claim 3, it is characterized in that,

The first area forms regular hexagon on the surface of the epitaxial layer, and the inscribed circle diameter of the regular hexagon is 16 micro- Rice, first preset interval are 16.5 microns.

7. the method according to claim 1, wherein

The region of first conduction type is N-type semiconductor, and the region of second conduction type is P-type semiconductor.

8. the method according to claim 1, wherein

Ohmic contact is formed between the region and the metal layer of second conduction type.

9. the method according to claim 1, wherein

The diode further includes cathode electrode, and the cathode electrode is connect with the substrate away from the side of the epitaxial layer； Ohmic contact is formed between the cathode electrode and the substrate.

10. a kind of Schottky diode preparation method characterized by comprising

Form substrate；

The epitaxial layer of the first conduction type is formed over the substrate；

The region of several second conduction types, second conduction type are formed away from the side of the substrate in the epitaxial layer Region and first conductivity type regions between form PN junction；Wherein, second conductivity type regions include several One region and second area, the first area are greater than the width of the second area along the width of the epi-layer surface, often Several second areas are equipped between two adjacent first areas, the first area is arranged according to the first preset interval, described Second area is arranged according to the second preset interval；

Schottky contact metal is formed away from the side of the substrate in the epitaxial layer.

Technical field

This application involves electronic technology fields more particularly to a kind of Schottky diode and preparation method thereof.

Background technique

In electronic circuit, the application range of diode is relatively broad.When diode is in the conductive state, it is understood that there may be The abnormal work situation of normal current working condition and accidental surge current.In the abnormal work of surge current, two Pole pipe may be overshooted there is a phenomenon where instantaneous energy and chip temperature increases, situations such as so as to cause diode fails.

Currently, the PN junction formed by P-type semiconductor in diode and N-type semiconductor, make PN junction diode by It is opened when inrush current shock, to make diode that there is lower resistivity and higher current capacity, to play pair The protective effect of diode.

But in Schottky diode, the setting of unreasonable PN junction can excessively occupy the face of original schottky junction Product, to influence the conduction voltage drop under diode normal current working condition, influences the conduction property of diode.

Summary of the invention

The embodiment of the present application provides a kind of Schottky diode and preparation method thereof, reasonable to provide a kind of PN junction setting Schottky diode.

A kind of Schottky diode provided by the embodiments of the present application, including substrate, epitaxial layer and metal layer；

The epitaxial layer is formed on the substrate, and the epitaxial layer is the region of the first conduction type；

The epitaxial layer is equipped with the region of several second conduction types, second conductive-type away from the side of the substrate PN junction is formed between the region of type and the region of first conduction type；Wherein, if second conductivity type regions include Dry first area and second area, the first area are greater than the width of the second area along the width of the epi-layer surface It spends, several second areas is equipped between every two adjacent first area, the first area is arranged according to the first preset interval, The second area is arranged according to the second preset interval；

The metal layer is formed in the side that the epitaxial layer deviates from the substrate, and the surface of the epitaxial layer is except described the Region except the region of two conduction types forms schottky junction with the metal layer.

A kind of Schottky diode preparation method provided by the embodiments of the present application, comprising:

Form substrate；

The epitaxial layer of the first conduction type is formed over the substrate；

The region of several second conduction types is formed away from the side of the substrate in the epitaxial layer, described second is conductive PN junction is formed between the region of type and first conductivity type regions；Wherein, if second conductivity type regions include Dry first area and second area, the first area are greater than the width of the second area along the width of the epi-layer surface It spends, several second areas is equipped between every two adjacent first area, the first area is arranged according to the first preset interval, The second area is arranged according to the second preset interval；

Schottky contact metal is formed away from the side of the substrate in the epitaxial layer.

A kind of Schottky diode and preparation method thereof that the embodiment of the present application proposes can bring it is following the utility model has the advantages that

1, by the way that the width and the first preset interval of first area is rationally arranged, schottky junction can not excessively occupied Area in the case where, increase the width of PN junction as far as possible, reduce the cut-in voltage of PN junction, reduce the function in the case of surge current The raising of rate loss and diode junction temperature, to improve the Antisurge current ability of diode；Meanwhile, it is capable to keep diode Conduction property under good normal current working condition.

2, by the way that the width and the second preset interval of second area is rationally arranged, the reverse leakage of diode can be reduced Size is flowed, the performance of diode is promoted, optimizes the structure of diode, while not influencing the normally pressure drop of diode, is kept Good forward conduction performance.

3, by the way that first area is shaped to regular hexagon in epi-layer surface, it is formed by the boundary of PN junction Angle is larger, and is not easy to concentrate electric field, so as to avoid increasing the reverse leakage current of diode.

4, by the way that first area is shaped to regular hexagon in epi-layer surface, by second area in superficies It is shaped to the ring hexagon around first area, enables first area and second area in reasonable situation, to the greatest extent The area that itself may be increased realizes close paving structure on the surface of epitaxial layer, to increase the Antisurge current ability of diode.

Detailed description of the invention

The drawings described herein are used to provide a further understanding of the present application, constitutes part of this application, this Shen Illustrative embodiments and their description please are not constituted an undue limitation on the present application for explaining the application.In the accompanying drawings:

Fig. 1 is the PN junction cut-in voltage and Antisurge current ability relationship of Schottky diode provided by the embodiments of the present application Schematic diagram；

Fig. 2 is a kind of Schottky diode cross-sectional view provided by the embodiments of the present application；

Fig. 3 is another Schottky diode cross-sectional view provided by the embodiments of the present application；

Fig. 4 is another Schottky diode cross-sectional view provided by the embodiments of the present application；

Fig. 5 is that the normally pressure drop of Schottky diode provided by the embodiments of the present application is shown with PN junction cut-in voltage relationship It is intended to；

Fig. 6 is the second preset interval and diode of the second area of Schottky diode provided by the embodiments of the present application The relation schematic diagram of normally pressure drop；

Fig. 7 is electric current of the diode under reverse blocking operating mode and voltage relationship schematic diagram；

Fig. 8 is another Schottky diode cross-sectional view provided by the embodiments of the present application.

Specific embodiment

To keep the purposes, technical schemes and advantages of the application clearer, below in conjunction with the application specific embodiment and Technical scheme is clearly and completely described in corresponding attached drawing.Obviously, described embodiment is only the application one Section Example, instead of all the embodiments.Based on the embodiment in the application, those of ordinary skill in the art are not doing Every other embodiment obtained under the premise of creative work out, shall fall in the protection scope of this application.

In mixing PN junction Schottky diode (calling " diode " in the following text), under normal current working condition, due to Schottky Barrier height is far below PN junction Built-in potential, therefore, when electric current passes through there was only schottky junction unlatching, diode only passes through Schottky Knot carries out current lead-through.In the abnormal work of surge current, PN junction is opened, and diode can pass through PN junction and schottky junction It is common to carry out current lead-through, so that diode is able to bear instantaneous high current, without because the reasons such as fever influence diode Performance, to enhance the Antisurge current ability of diode.

In the diode, the size (e.g., width, area etc.) of PN junction and its cut-in voltage are negatively correlated relationship.And such as Fig. 1 Shown, axis of abscissas indicates that PN junction cut-in voltage, axis of ordinates indicate the size for the transient high-current that diode is able to bear, i.e., The Antisurge current ability of diode.As shown in Figure 1, the Antisurge current ability of the cut-in voltage of PN junction and diode is at negative Pass relationship.Therefore, the Antisurge current ability positive correlation of the size of PN junction and diode.In order to enhance the anti-of diode Surge current ability can increase the size of PN junction in diode as far as possible.

But the increase of the size due to PN junction, it will lead to the reduction of the area of corresponding schottky junction.Due in two poles Under the normal current working condition of pipe, diode only carries out current lead-through, therefore, the normal current of diode by schottky junction Conduction property depends on the size of schottky junction, if the area of schottky junction reduces, will lead to diode in normal electricity The conduction voltage drop flowed under working condition increases, to reduce the conduction property of diode.

Therefore, in order to guarantee conduction property of the diode under normal current working condition, while enhancing the anti-of diode Surge current ability, the size of PN junction need to be rationally arranged in diode.

Fig. 2 is a kind of Schottky diode cross-sectional view provided by the embodiments of the present application.Fig. 3 is provided by the embodiments of the present application Another Schottky diode cross-sectional view.

As shown in Fig. 2, diode 10 may include substrate 12, epitaxial layer 13 and metal layer 19.

Specifically, may include in diode 10 containing impurity and be the first conduction type silicon carbide substrates 12；Substrate 12 On be formed with the epitaxial layer 13 of the first conduction type；Epitaxial layer 13 is equipped with several second conduction types away from the side of substrate 12 Region 14 forms PN junction 15 between the region 14 of second conduction type and the epitaxial layer 13 of the first conduction type；Epitaxial layer 13 is carried on the back Side from substrate 12 is formed with metal layer 19, deviates from the surface of 12 side of substrate, the area of the second conduction type in epitaxial layer 13 The first Ohmic contact 18, area of the surface of epitaxial layer 13 in addition to the first Ohmic contact 18 are formed between domain 14 and metal layer 19 Domain forms schottky junction 16 with metal layer 19.

Wherein, the region 14 of the second conduction type includes several first areas 141 and second area 142.First area 141 It is greater than the width P of second area 142 along the width W on 13 surface of epitaxial layer.In the embodiment of the present application, the firstth area in diode 10 Domain 141 can be regular shape, including regular polygon, circle etc. in the shape that the surface of epitaxial layer 13 is formed.Therefore, first area 141 width is often referred to length represented by length represented by the inscribe diameter of a circle of regular polygon or circular diameter. And the width of second area 142 then indicates, connection side of the second area 142 between two adjacent first areas 141 is upward Length.Several second areas 142 are equipped between every two adjacent first area 141, first area 141 is default according to first It is spaced S arrangement, second area 142 is arranged according to the second preset interval N.

As shown in Figures 3 and 4, Fig. 3 is the transverse sectional view of diode, i.e., is formed by the firstth area on 13 surface of epitaxial layer Domain 141, second area 142 and schottky junction 16 arrangement schematic diagram, Fig. 4 be diode direction AA ' along Fig. 3 section view Figure.Regular hexagon in Fig. 3 is first area 141, around the ring hexagon (ring structure i.e. as shown in the figure) of regular hexagon For second area 142.The width of first area 141 in Fig. 3, that is, regular hexagon inscribe diameter of a circle as a result, second area 142 Width be along the connection direction of two adjacent regular hexagons, the width of ring structure.

It should be noted that the shape and layout type etc. of first area 141 and second area 142 shown in Fig. 3, A kind of only example for proposing of the embodiment of the present application, the application to concrete shape used by first area and second area and Layout type etc. is without limitation.

Further, since the effect of epitaxial layer 13 is the reverse BV for undertaking diode 10, and diode 10 is reversed The doping concentration of blocking voltage and epitaxial layer 13 is negatively correlated relationship, therefore, in order to increase diode 10 under reverse blocking The doping concentration of pressure resistance, epitaxial layer 13 can be lower, concretely 1x10¹⁴~1x10¹⁷cm^-3.And substrate 12 is to the anti-of diode 10 It is not had an impact to blocking voltage, and substrate 12 can introduce additional resistance, therefore, the doping concentration of substrate 12 can be higher, tool Body can be 1x10¹⁷~1x10¹⁹cm^-3.Then, the doping concentration of epitaxial layer 13 can be lower than the doping concentration of substrate 12.

In the embodiment of the present application, the first preset interval can width based on first area 141 and schottky junction 16 face Product determines that the second preset interval can be determined based on the reverse leakage current size of diode 10.

If there are various sizes of PN junctions in diode, when diode meets with surge current, various sizes of PN junction meeting It is successively opened according to the sequence of size from big to small.Therefore, in the embodiment of the present application, when diode 10 meets with surge current, First area 141 can first open.Then, the width of first area 141 can determine the Antisurge current ability of diode 10.

In the embodiment of the present application, in order to guarantee conduction property of the diode 10 under normal current working condition, simultaneously The Antisurge current ability for enhancing diode 10, when first area 141 is arranged, can width based on first area 141 and The area of schottky junction 16 determines the first preset interval.Wherein, the width of first area 141 may be configured as 2~21 microns.

Specifically, as shown in Figure 3, Figure 4, the embodiment of the present application is with 2A, and under the conditions of 1200V, first area 141 is in epitaxial layer Surface formed shape be regular hexagon diode for be illustrated.Fig. 5 is normally pressure drop and the PN of diode Tie cut-in voltage relation schematic diagram.As shown in figure 5, axis of abscissas indicates the normal pressure drop of diode, axis of ordinates indicates two poles The unlatching pressure drop of PN junction in pipe, the curve in figure indicate that diode in first area there is corresponding width W and first to preset In the case where being spaced S, by testing the normal pressure drop of resulting corresponding diode and unlatching pressure drop (corresponding two poles of PN junction The Antisurge current ability of pipe).As shown in Figure 5, in order to make diode that there is good ducting capacity, while having good anti- Surge current ability, the width of the first area of the corresponding diode of point where " ☆ " symbol in figure and first it is default between Every the optimum point weighed between normal ducting capacity and Antisurge current ability for diode.

Therefore, in the embodiment of the present application, under the conditions of 2A, 1200V, as shown in figure 3, the first area in diode 10 141 form the shape of regular hexagon on the surface of epitaxial layer 13, and are evenly spaced in epitaxial layer 13.In this case, It can be obtained by Fig. 5, when the width W (that is, inscribe diameter of a circle of regular hexagon) of first area 141 is 16 microns, between first is default When S is 16.5 microns, diode 10 can obtain lower normally pressure drop simultaneously and lower PN junction opens pressure drop (i.e. higher Antisurge current ability).

It should be noted that the embodiment of the present application, only with 2A, under the conditions of 1200V, the first area of diode is in epitaxial layer Surface formed regular hexagon shape for be illustrated, the shape of first area unmentioned for other the embodiment of the present application Shape and layout type etc., can be determined by above-mentioned identical method corresponding first area width and first it is default between Every.

In the embodiment of the present application, by comprehensively considering the width of first area and the area of schottky junction, to determine The first preset interval between two adjacent first areas.This arrangement mode can be in the limited face of the chip of diode On the basis of product, the reasonable width that first area is set, and first is reasonably arranged according to the first preset interval determined The position in region enables diode to obtain good normally performance and good Antisurge current ability, energy simultaneously The structure for enough optimizing diode, improves the working performance of diode.

Specifically, Fig. 6 is the second preset interval and two of the second area 142 of diode 10 provided by the embodiments of the present application The relation schematic diagram of the normally pressure drop of pole pipe.As shown in fig. 6, axis of abscissas indicates the normally pressure drop of diode, indulge Reference axis indicates the conducting electric current of diode, and curve indicates have the diode of the second different preset intervals is corresponding normally to lead Logical pressure drop and conducting electric current.It will be appreciated from fig. 6 that second with diode is default in the case where the width of second area is constant The normally pressure drop of the increase at interval, diode reduces, that is, the forward conduction performance boost of diode.

But the second preset interval of diode is also related with the reverse leakage current of diode.Fig. 7 is the embodiment of the present application Electric current of the diode of offer under reverse blocking operating mode and voltage relationship schematic diagram.As shown in fig. 7, axis of abscissas is two The reversed pressure drop of pole pipe, axis of ordinates is the reverse leakage current of diode, between the second of the second area of N expression diode is default Every curve indicates in figure, and in the case where the width of second area is constant, the diode of different second preset intervals is corresponding Reverse leakage current under reversed pressure drop.As shown in Figure 7, when the second preset interval is from when increasing to 5 microns for 2 microns, diode exists Reverse leakage current size under 1200V voltage increases two orders of magnitude.That is, the feelings constant in the width of second area Under condition, the size positive correlation of the reverse leakage current of the size and diode of the second preset interval.Between being preset with second Every increase, the reverse leakage current of diode increases.

Therefore, in the embodiment of the present application, the width P of second area can take lesser value as far as possible, and second area it Between the second preset interval N can based on the reverse leakage current size of diode determine.Specifically, can be answered for the difference of diode With demand, to determine the demand to the reverse leakage current size of diode, so that it is determined that the second preset interval of diode.Its In, the width of second area can be 0~3 micron.

Such as different busbar voltage designs can propose different stress levels demands, and circuit to diode in circuit Its requirement to the leakage current of diode is determined to the limit value of power loss in the shutdown mode.When the electric leakage of diode Size requirements are flowed in 1uA or less, and the second preset interval of second area can be 3 microns, when the leakage current of diode is wanted It asks in 10uA hereinafter, the second preset interval of second area can be 4~5 microns.

In the embodiment of the present application, by reducing the width of second area, it can reduce the chip area in diode, drop The cost of low diode.By the second preset interval of increase second area, the forward conduction voltage drop of diode can be reduced, from And be conducive to improve the forward conduction performance of diode.

In the embodiment of the present application, as shown in figure 3, second area 142 can surround first area on the surface of epitaxial layer 13 141 form ring structure, also, are directed to each first area 141, and several second areas 142 may be present with the first area 141 Centered on, it is arranged successively according to the direction that center dissipates around, and the secondth area between every two adjacent first area 141 Domain 142 can uniformly arrange.Wherein, the second area 142 between every two adjacent first area 141 can be strip structure, adjacent Two close strip structures mutually extend, and can meet at a bit, to form the second area of the ring structure around first area.

Specifically, the shape of first area 141 is usually regular shape, including regular polygon, circle etc..Due to when two poles When pipe is in reverse blocking state, the position of PN junction can establish electric field in the diode, and there are curvature effects for electric field.Namely It says, it is smaller that the boundary of PN junction is formed by angle, the easier concentration of electric field, and electric field strength increases, the reverse leakage current of diode Also can increase accordingly.Therefore, in order to avoid the reverse leakage current of increase diode, first area 141 is on 13 surface of epitaxial layer Acute angle should be avoided as far as possible by being formed by shape.That is, when first area 141 is positive the side n shape, n > 3.

Wherein, when first area 141 is when the shape that 13 surface of epitaxial layer is formed is regular hexagon, due to regular hexagon Interior angle is 120 degree, can be divided exactly by 360 degree, and therefore, several first areas 141 can realize Mi Pu knot on the surface of epitaxial layer 13 Structure.Such design is simpler, and can increase first area as far as possible in the width and area of epi-layer surface, to increase The Antisurge current ability of strong diode.

Specifically, the quantity of the second area between every two adjacent first area can be true by S=P*X+N* (X+1) It is fixed, wherein S is the first preset interval, and P is the width of second area, and N is the second preset interval, and X is two adjacent firstth areas The quantity of second area between domain.As shown in figure 3,3 second areas can be equipped between every two adjacent first area, such as Shown in Fig. 8,2 second areas can be equipped between every two adjacent first area.

Specifically, the region of the first conduction type can be N-type semiconductor, the region of second conduction type can be p-type Semiconductor.

Specifically, cathode electrode 11, which is formed in substrate 12, to deviate from as shown in Fig. 2, diode 10 further includes cathode electrode 11 The side of epitaxial layer 13；The second Ohmic contact 17 is formed between cathode electrode 11 and substrate 12.

The above are Schottky diodes provided by the embodiments of the present application, are based on same invention thinking, the embodiment of the present application The preparation method of corresponding Schottky diode is additionally provided, is specifically included:

Form substrate.Specifically, N-type silicon carbide can be used to do substrate.

The epitaxial layer of the first conduction type is formed on the substrate.Specifically, epitaxial layer can be made of N-type silicon carbide.Wherein, The doping concentration of epitaxial layer is lower than the doping concentration of substrate.

Form the regions of several second conduction types away from the side of substrate in epitaxial layer, the region of the second conduction type with PN junction is formed between the epitaxial layer of first conduction type.Wherein, the region of the second conduction type includes several first areas and Two regions, first area is greater than the width of second area along the width of epi-layer surface, between every two adjacent first area Equipped with several second areas, first area is arranged according to the first preset interval, and second area is arranged according to the second preset interval.

Specifically, can deposited masking layer, photoetching and etching mask layer formation pattern transfer on epitaxial layer.Ion is carried out again Injection, so that the privileged site on the surface of epitaxial layer forms the region of the second conduction type.Wherein, the area of the second conduction type Domain can be p type impurity doping, and impurity type can be aluminium or boron.

Later, metal ohmic contact can be formed in the overlying regions of the second conduction type.Specifically, upper one can remained with The epi-layer surface deposited metal of mask patterns in step process, anneals to metal, straight with epi-layer surface in metal The interface of contact forms Ohmic contact, finally removes mask layer and excess metal thereon with wet etching.

S104: Schottky contact metal is formed away from the side of substrate in epitaxial layer.Specifically, can be at the top of epitaxial layer Deposited metal, then low-temperature annealing form Schottky contacts on the surface of epitaxial layer.

Later, it can anneal in deposited metal under substrate to the metal under substrate, the shape between metal and substrate surface At Ohmic contact.

It should be noted that the part being not described in detail in this preparation method, such as first area and the width of second area Degree, arrangement mode etc. can refer to associated description above, and details are not described herein by the application.

The above description is only an example of the present application, is not intended to limit this application.For those skilled in the art For, various changes and changes are possible in this application.All any modifications made within the spirit and principles of the present application are equal Replacement, improvement etc., should be included within the scope of the claims of this application.